I don't know why. The pressures are high enough as is. There was a 357 Maximum in the 80's, and I heard it was a throat burner. Whatever its problems, it did not last long.
I don't need more power than a 44 Magnum in a pistol. Handcannons are for those who want them: I decided that they were too much fun for me. If I think I need more power I will get it in a rifle.
If I'm not shooting, I'm reloading.